Like dreaming of walking through a world they've not yet experienced, the retinas of neonatal mice practice for what mature eyes must later process by generating spontaneous patterns of activity that mimic the perception of directional movement through space, according to a new study. Essential functions in the mammalian visual system, including the ability to locate objects and detect motion, are present even at the first onset of vision. Optic flow, the perceived relative motion of objects and surfaces that seemingly stream by a field of vision during movement, is one of these functions. However, how the visual system organizes its functional characteristics before visual sensory experience is even possible remains unclear. And, while previous studies have revealed spontaneous retinal activity prior to functional vision, the role of this spontaneous activity in visual system development is unknown. Xinxin Ge and colleagues examined the spontaneous activity of ganglion cells in mice at multiple ages throughout development in vivo and discovered an intrinsic mechanism in the developing retina that prepares the downstream visual system for motion detection before the newborn mice can see. According to Ge et al., spontaneous waves of retinal activity during this transient window flow in the same pattern as would be produced if the mouse was physically moving through the environment. This patterned, spontaneous activity effectively trains the visual system and the associated brain circuits to process directional information and to interpret movement through space at eye opening.
